Elevator protective device



June 19, 1951 c. R. SCHMlDT 2,557,843

ELEVATOR PROTECTIVE DEVICE Filed July 15, 1950 3 sheetssheet 1 HIGH J. .E. l L67 I INVENTOR.

CHfl/PlfS A? Saw/W07 BY H/S ATTORNEYS ww w June 19, 1951 c. R. SCHMIDT 2,557,843

7 ELEVATOR PROTECTIVE DEVICE Filed July 15, 1950 z Sheets-Sheet 2 40 I5 628 a? f If 47 W" =1 7/ ,0 2

I 66 M i 4" X) V I8 INVENTOR.

C'AWPZS E Sew/war BY HIS ATTORNEYS ww w June 19, 1951 Filed July 15, 1950 C. R. SCHMIDT ELEVATOR PROTECTIVE DEVICE 3 Sheets-Sheet 3 5 r' 10 fig 73 1.? 19

fi- -r7 f n 32 2 k 7 J9 14 /6 i) L INVENTOR.

(kw/P455 r? Saw/W07 BY HIS ATTORNEYS Patented June 19, 1951 UNITED STATES PATENT OFFICE ELEVATOR PROTECTIVE DEVICE Charles B. Schmidt, East Paterson, N. J., as-

signor to Martin Elevator 00., Inc., New York, N. Y., a corporation of New York Application July 15, 1950, Serial No. 174,038

9 Claims. 1

The present invention relates to protective systems for elevators and more particularly to protective systems for direct current operated elevators. More particularly, the invention embodies a mechanism by means of which running away of the elevator car is prevented under circumstances such as interruption of the power supply due to opening of the feed lines while the elevator car is in motion.

It is generally known that in direct current operated elevator systems difficulty is occasionally experienced with the running away of a car under certain conditions. For example, it is conventional to counterweight a car to 40 of the maximum car load. With such a counterweighted car, if the car is lightly loaded and traveling upwardly or heavily loaded and going downwardly, and the current is interrupted. (as a result, for example, of the blowing of a fuse) the car will continue to move because the weight of the counterweight or car drives the motor as a generator and the generated current will continue to hold the brake shoes open. In accordance with the present invention, it is an object to provide a mechanism by means of which the running away of a car under the aforementioned conditions will be prevented.

The foregoing object and other objects are attained by utilizing at least a portion of the power supply circuit (in particular, the portion should include the fuses) as a circuit for an alternating current which serves as a supervisory or guardian circuit and which, when interrupted, insures that the coil or coils of the brake operating mechanism will be de-energized to permit the brake to grip the brake drum and bring the elevator car to a stop.

Several ways of accomplishing the foregoing will now be described in connection with the accompanying drawings, wherein Figure 1 is a diagrammatic representation of a form of circuit in which a brake mechanism is controlled in the above fashion;

Figure 2 is a diagrammatic illustration of a modified version of the system of Figure l, in which the change of impedance of the primary circuit of the transformer is utilized in the oathode circuit of the vacuum tube;

Figure 3 is a further modification of a protective circuit constructed in accordance with the present invention, wherein the line is used as a coupling for the alternating current that is utilized as the supervisory or guardian force;

Figure 4 is yet another modification wherein the line is used as a conductor for the detector 2 relay circuit operated by the alternating current;

Figure 5 is a further modification of the invention, wherein the line is used as one leg of a Wheatstone bridge, the unbalance of which accomplishes the protective operation desired; and

Figure 6 is yet another modification of the invention, wherein the variation of the Wheatstone circuit is utilized.

Referring to the drawings, in all of the figures a power supply is illustrated at 10 in the form of direct current mains connected through fuses H to wires !2 and I3 which form the operating circuit of a direct current motor 14 having a field IS. A suitable circuit breaker l3a of conventional form is provided and in accordance with conventional practice, the motor shaft is provided with a brake drum, the brake shoes of which are held in inoperative position by means of a coil 16 that is connected across the wires l2 and I3 by means of wires ll. All of the foregoing elements are conventional with existing direct current operated elevator circuits and are shown in each of the figures of the accompanying drawings.

In accordance with the present invention, the circuit H of the coil I6 is opened upon failure of the power supply (as, for example, by blowing either or both of the fuses H) by means of a supervisory or guardian circuit now to be described. A suitable high frequency oscillator I8 is energized through wires l3 and '20 connected to the power supply Hi. The output of the oscillator is supplied to the primary 2! of a transformer 22 by means of wires 23 and 24. Condenser 25 and resistance 26 are included in the output wire 23, and the input of a vacuum tube 21 is connected across the primary 2! by means of wire 28 which is connected to the grid of the vacuum tube and a wire 29 which is connected to the cathode and which includes a grid bias source 36. The plate circuit 3! of the vacuum tube 2'! includes a relay coil 32 and is connected through wire 33 to the wire 25] and the power supply.

The secondary 34 of the transformer 22 is connected across the wires l2 and I3 through a condenser 35. Relay contacts 35 are included in the wires [1, the contacts being actuated by the coil 32. The wires ll extend at 3'! to a series switch on the contactor panel. In order to properly adjust the impedance of the line, parallel connected condenser 33 and inductance 39 are connected in the circuit of wire l3.

The operation of the above mechanism under 3 normal conditions will be the operation of the normal direct current elevator mechanism. In addition, the high frequency oscillator l8 produces a guardian or supervisory alternating current which is impressed upon the primary 2! and, through the secondary, upon the line and motor connections I2 and I3, which include the fuses l I. The high frequency voltage drop across the primary 2i is applied across the grid and cathode of tube 21, which is biased to a slightly less negative value than cutofi and preferably permits a slight amount of plate current to flow. This current is not sui'ficient to energize the coil 32' to cause the opening of the. normally closed contacts 36. The condenser 38- and inductance 39 are selected to be antiresonant at the frequency of the oscillator (that is, to have-a high'resistive impedance at the frequency to which it is tuned) so that the motor circuit presents a high-impedance to the high frequency current. The power mains, however, including the fuses H offer. a.

low impedance to the high frequency current, keeping the primary impedance of the transformer 22 low compared to the series resistor 26.. Thus thehigh frequency drop across'the trans.

former primary is small and.v since the: vacuum tube 21 is biased to aboutcutoiflthe-plate circuit and the relay coil 32 are not energized. Under these conditions the brakecoil i6. canbe energized. by the series contacts on the contactor panel, and the normal operation of the elevator takes place. If desired, the anti-resonant circuit. afforded by the-condenser 38. and inductance 3%. maybe replaced by an inductance having a sufficiently high impedance to prevent the motor circuitfrom keeping the device from operating.

In the event that either of the: fuses H blows, the shorting effect of the powermains Will. be absent-from the secondary 3 5, and theimpedance of the primary'z i willimmediately increase. The highfrequency voltage drop across the primary will' thus increase and thus cause an increase in the plate: current which willenergizethe relay 32 andopen the contacts 36.

With reference to Figure 2, the system isquite similar to the-system shown in Figure 1, except that the change of the impedanceof the circuit of the primary 25' is used in the cathode circuit of the vacuum tube 2'1. When this impedance is low, there is only a slight degeneration in the tube. With the low series plate circuit impedance and the high resultant grid voltage, there is a relatively highplate current. When the fuses blow or thepower mains open, the primary impedance becomes high, causing degeneration in the tube and reducing the resultant grid voltage. The impedance of the plate circuit is increased, causing the plate current to decrease, as a result of which the relay contacts 38 open and the brake coil I8 is thus de-energized. The impedance of the power mains can be reducedby placing a condenser dilacross the line or, if desired, a series inductanc ti and capacitance 32 maybe connected across the line and tuned to the high frequency generated by the oscillator.

With reference to Figure 3, the basic elevator circuit of Figures 1 and 2 is again utilized, high frequency oscillator 18 being connected to a transformer 43, the secondary of which is connected in the circuit wire l2. A second transformer &4 is connected in the circuit wire l3, and its secondary is connected to the coil 32 through wires 45. If desired, the condenser 40 may again be used in the power supply. In this system, the

line is used as a' coupling for the high frequency current which is impressed upon it by the transformer 43 and opening of the circuit interrupts the power supplied to the coil 32 from the transformer 44. In this circuit a condenser 46 is connected across the wires 12 and [3 to provide a path for the high frequency current when the motor line contactor is open. As an alternative, the condenser it may be utilized, this condenser shunting the line to give a path for the oscillator frequency. With this arrangement the elevator isprotected only against the opening of the main switch 47 and-the blowing of either of the fuses l I.

In the form of the invention illustrated in Figure 4, the line is used as a conductor for the detector relay circuit. Here the oscillator I8 is connected to wire it by means of a wire 48 and, again, the circuit characteristics are such that the anti-resonance of the capacitance inductance mechanism 38 and 3t prevents the how of any but a weak current insuficient to cause operation of the mechanism, whereas the main flow of. the

alternating current is through the fusesiand the main switch di in power line l0 (which mayop tionally have the capacitance 613 connected across. The detector relay 32' is thus in series with.

it). the oscillator, and the fuses, switches and'power.

mains are used as conductors of the relay current-.- The antiresonant circuit in the motor side of'the: line prevents the motor circuit from providing a.

line is connected through condensersfi-il-and wires 55 to one leg of a Wheatstone bridg indicated generally at 5|. A high frequency oscillator l8 serves to supply a high frequency'current acrossthe points 52 and 53 of the bridge. From52 the current flows through impedances 54 and 55, and

from point 53 current flows through impedance 56 and the impedance'of the lines which is connccted through the wires 5%. bridged across points 5'"? and 58, andthus-in nor-- mal operation, no current will flow through the coil because of the balance of the system; When, however, the impedance of the line changes; by reason ofthe blowing of fuses l l or the opening of the line switch 57, balance is disturbed and current through-the coil 32 will cause the opening of the normally closed contacts as.

In Figure 6 there is illustrated a modified-version of the bridge relationship of Figure 5, wherein the normal elevator circuit above described has connected thereto the" wires 59 through condensers 9 to keep direct current out of the bridge. The relay coil'32 is connected with respect to impedances 59, 6d, and GI in such fashion that there is a normal balance upon generation of high frequency oscillations by means of the oscillator I31v Impedances 59 and. 60 are used to obtain balance under normal'conditions, and again th antiresonance of. the motor circuit provided by the capacitance and. inductiances 38 and 39. prevent the bridge circuit. from being affected by the motor circuit. Upon. a change in the line impedance, the bridge circuit. is unbalanced, and the relay coil 32 is. energized. to actuate the contact 35 as described in connection with Figure 5.

The systems of Figures 5' and 6 may. also be. utilized by balancing for the open line condition,

The coil 32' is so that in the normal operation of the elevator the bridges will be unbalanced. In these circumstancesjthe blowing of the fuses or the opening of the switch 41 will cause the bridge to balance and thus operate the detector relay coil 32. The unbalancing of the bridge will cause a normal current flow to hold the relay in the desired closed position during operation.

While the invention has been described with specific reference to the accompanying drawings, it is not to be limited save as defined in the appended claims.

I claim:

1. A protective device for elevator control circuits and the like, comprising power mains for supplying power, an electric motor for operating an elevator car, a normally closed brake and operating coil therefor for preventing movement of the car, said brake operating coil having a circuit therefor, circuit connections for operating the motor and brake coil circuit from the power mains, fuses in the circuit connections, means for impressing an alternating current upon at least that portion of the connections including the fuses, means for interrupting the circuit of the brake operating coil, and means responsive to a change in the electrical characteristics of the circuit connections to actuate the last named interrupting means by the alternating current.

2. A protective device for elevator control circuits and the like comprising power mains for supplying power, an electric motor for operating an elevator car, a normally closed brake and operating coil therefor for preventing movement of the car, said brake operating coil having a circuit therefor, circuit connections for operating the motor and brake coil circuit from the power mains, fuses in the circuit connections, means for impressing an alternating current upon at least that portion of the connections including the fuses, means for interrupting the circuit of the brake operating coil, and means responsive to interruption of the circuit connections to actuate the last named interrupting means by the alternating current.

3. A protective device for elevator control circuits and the like, comprising power mains for supplying power, an electric motor for operating an elevator car, a normally closed brake and operating coil therefor for preventing movement of the car, said brake operating coil having a circuit therefor, circuit connections for operatin the motor and brake coil circuit from the power mains, fuses in the circuit connections, means energized by the power mains for generating an alternating current, means for impressing the alternating current upon at least that portion of the connections including the fuses, means for interrupting the circuit of the brake operating coil, and means responsive to a change in the electrical characteristics of the circuit connections to actuate the last named interrupting means by the alternatin current.

4. A protective device for elevator control circuits and the like, comprising power mains for supplying power, an electric motor for operating an elevator car, a normally closed brake and operating coil therefor for preventing movement of the car, said brake operatin coil having a circuit therefor, circuit connections for operating the motor and brake coil circuit from the power mains, fuses in the circuit connections, means energized by the power mains for generating an alternating current, means for impressing the alternating current upon at least that portion of the connections including the fuses, means for preventing the operating circuit connections of the motor from causin the actuating of the device, means for interrupting the circuit of the brake operating coil, and means responsive to a change in the electrical characteristics of the circuit connections to actuate the last named interrupting means by the alternating current.

5. A protective device for elevator control circuits and the like, comprising power mains for supplying power, an electric motor for operating an elevator car, a normally closed brake and operating coil therefor for preventing movement of the car, said brake operating coil having a circuit therefor, circuit connections for operating the motor and brake coil circuit from the power mains, fuses in the circuit connections, means for impressing an alternating current upon at least that portion of the connections including the fuses, contacts in the circuit of the brake operating coil, and means responsive to a change in the electrical characteristics of the circuit connections to actuate the contacts by the alternating current.

6. A protective device for elevator control circuits and the like, comprising power mains for supplying power, an electric motor for operating an elevator car, a normally closed brake and operating coil therefor for preventing movement of the car, said brake operating coil having a circuit therefor, circuit connections for operating the motor and brake coil circuit from the power mains, fuses in the circuit connections, means for impressing an alternating current upon at least that portion of the connections including the fuses, contacts in the circuit of the brake operating coil, and means responsive to an interruption of the current from the power mains to actuate the contacts by the alternating current.

'7. A protective device for elevator control circuits and the like, comprising power mains for supplying power, an electric motor for operating an elevator car, a normally closed brake and operating coil therefor for preventing movement of the car, said brake operating coil having a circuit therefor, circuit connections for operating the motor and brake coil circuit from the power mains, fuses in the circuit connections, means for impressing an alternating current upon at least that portion of the connections including the fuses, contacts in the circuit of the brake operating coil, and means responsive to a change in the impedance of at least that portion of the connections including the fuses, to actuate the contacts by the alternating current.

8. A protective device for elevator control circuits and the like, comprising power mains for supplying power, an electric motor for operating an elevator car, a normally closed brake and operating coil therefor for preventing movement of the car, said brake operating coil having a circuit therefor, circuit connections for operating the motor and brake coil circuit from the power mains, fuses in the circuit connections, means for generating a high frequency alternating current, a transformer, means for connecting the primary of the transformer to the generating means, means for connecting the sec ondary of the transformer to the circuit connections, an antiresonant device in the circuit connections between the last named connections and the elevator operating means, a vacuum tube having a cathode, plate and grid, means connecting the primary of the transformer across the rid and cathode, a relayicoilin. thev plate circuit of the vacuumv tube, and: contactsin the circuitrof the brake operatin coil and operated by the relaycoil for opening the last: named circuit upon a change in impedance of the circuit connections.

9. A protective device for elevator controlic-ircuits and the like, comprising power mains for supplying power, an electric motor for operating an elevator car, anormally closed brakeandoperating coil therefor for preventing movement of the car, said brake operating coil 'having a circuit therefor, circuit connections foroperating the'motor and brake coil circuit from thepowermains,- fuses in the circuit connections,- means for-generatinga high frequencyalternating current, a. transformer, means for connecting the primary of the transformer: to the generating! means, meansfor' connectin the secondary of. the transformer tov the circuit connections,- an,

antiresonantt device in the circuit connections between the last; named connections andithe--ele-- vator operating means, a vacuum: tube having: a cathode, plate and grid, the grid and cathode:

being connected in series with the primary of the transformer, and contacts in the circuit'of the brake operating coiland operated bythe relay coil for opening the last named circuit upon a change in impedance of the circuit connections.

CHARLES R; SCHMIDT.

No references cited; 

